Fig. 4.

Expression of the pcbC and penDE genes after the addition of conditioned broth. (A) Expression of the pcbC and penDE penicillin biosynthetic genes. The conditioned broth (10%) was added (+) to cultures at inoculation time (0 h) or 12 h or 24 h after the inoculation time. MilliQ water was added at the same percentage (10%) as for the control. RNA was extracted at 48 h. The transcripts from the β-actin gene were used as a control for the total RNA amount (see Fig. S2A in the supplemental material). Northern blots were hybridized with radioactively labeled pcbC, penDE, or β-actin probe and detected with a phosphorimager (Packard). The transcript levels were normalized, comparing the cpm provided by each mRNA to the β-actin mRNA radioactivity signal. (B) Quantitation of the radioactivity signal (cpm) provided in the Northern blot analysis shown in Fig. S2B. The transcript levels were normalized, comparing the cpm provided by each mRNA to the β-actin mRNA radioactivity signal. Data from panels A and B were subjected to one-way ANOVA, and the P value is indicated.